Matter is made of minute particles called atoms, and atoms are composed of even smaller components. These components have measurable properties, such as mass and electrical charge. Each atom has a positively charged nucleus surrounded by negatively charged electrons. The electric force between the nucleus and electrons holds the atom together. 178 B (9-12)

atom, force, interaction, mass, measurement, nucleus, small, surround

The atom's nucleus is composed of protons and neutrons, which are much more massive than electrons. When an element has atoms that differ in the number of neutrons, these atoms are called different isotopes of the element. 178 B (9-12)

composition, mass, nucleus, size

The nuclear forces that hold the nucleus of an atom together, at nuclear distances, are usually stronger than the electric forces that would make it fly apart. Nuclear reactions convert a fraction of the mass of interacting particles into energy, and they can release much greater amounts of energy than atomic interactions. Fission is the splitting of a large nucleus into smaller pieces. Fusion is the joining of two nuclei at extremely high temperature and pressure, and is the process responsible for the energy of the sun and other stars. 178 B (9-12)

bond, distance, fission, force, nucleus, scatter, size

Radioactive isotopes are unstable and undergo spontaneous nuclear reactions, emitting particles and/or wavelike radiation. The decay of any one nucleus cannot be predicted, but a large group of identical nuclei decay at a predictable rate. This predictability can be used to estimate the age of materials that contain radioactive isotopes. 178 B (9-12)

decay, emission, nucleus, radiation, rate, wave

Structure and properties of matter

teaching standard

spatial concepts

Atoms interact with one another by transferring or sharing electrons that are furthest from the nucleus. These outer electrons govern the chemical properties of the element. 178 B (9-12)

An element is composed of a single type of atom. When elements are listed in order according to the number of protons (called the atomic number), repeating patterns of physical and chemical properties identify families of elements with similar properties. This 'Periodic Table' is a consequence of the repeating pattern of outermost electrons and their permitted energies. 178 B (9-12)

outer, pattern, representation, spatialization

Bonds between atoms are created when electrons are paired up by being transferred or shared. A substance composed of a single kind of atom is called an element. The atoms may be bonded together into molecules or crystalline solids. A compound is formed when two or more kinds of atoms bind together chemically. 179 B (9-12)

atom, atomicity, bond, composition, crystalline, interaction, pairing

The physical properties of compounds reflect the nature of the interactions among its molecules. These interactions are determined by the structure of the molecule, including the constituent atoms and the distances and angles between them. 179 B (9-12)

Solids, liquids, and gases differ in the distances and angles between molecules or atoms and therefore the energy that binds them together. In solids the structure is nearly rigid; in liquids molecules or atoms move around each other but do not move apart; and in gases molecules or atoms move almost independently of each other and are mostly far apart. 179 B (9-12)

Carbon atoms can bond to one another in chains, rings, and branching networks to form a variety of structures, including synthetic polymers, oils, and the large molecules essential to life. 179 B (9-12)

A substance has characteristic properties, such as density, a boiling point, and solubility, all of which are independent of the amount of the sample. A mixture of substances often can be separated into the original substances by using one or more of the characteristic properties. 154 B (5-8)

composition, density, mixture, separation, solubility, substance

Substances react chemically in characteristic ways with other substances to form new substances (compounds) with different characteristic properties. In chemical reactions, the total mass is conserved. Substances often are placed in categories or groups if they react in similar ways; metals is an example of such a group. 154 B (5-8)

categorization, compound, group, mass, placement

Chemical elements do not break down by normal laboratory reactions such as heating, exposure to electric current, or reaction with acids. There are more than 100 known elements that combine in a multitude of ways to produce compounds, which account for the living and nonliving substances that we encounter. 154 B (5-8)

composition, current, exposure, scale

Motion and forces

teaching standard

spatial concepts

The motion of an object can be described by its position, direction of motion, and speed. That motion can be measured and represented on a graph.

direction, graph, motion, object, position, representation, speed

An object that is not being subjected to a force will continue to move at a constant speed and in a straight line. 154 B (5-8)

force, line, motion, object, path, straight

If more than one force acts on an object along a straight line, then the forces will reinforce or cancel one another, depending on their direction and magnitude. Unbalanced forces will cause changes in the speed or direction of an object's motion. 154 B (5-8)

balance, direction, force, line, magnitude, motion, speed, straight

Transfer of energy

teaching standard

spatial concepts

Energy is a property of many substances and is associated with heat, light, electricity, mechanical motion, sound, nuclei, and the nature of a chemical. Energy is transferred in many ways. 155 B (5-8)

light, motion, nucleus

Heat moves in predictable ways, flowing from warmer objects to cooler ones, until both reach the same temperature. 155 B (5-8)

flow, motion, spatial equilibrium

Light interacts with matter by transmission (including refraction), absorption, or scattering (including reflection). To see an object, light from that object--emitted by or scattered from it--must enter the eye. 155 B (5-8)

Objects have many observable properties, including size, weight, shape, color, temperature, and the ability to react with other substances. These properties can be measured using tools such as rulers, balances, and thermometers. 127 B (K-4)

balance, measurement, object, ruler, shape, size, thermometer

Objects are made of one or more materials, such as paper, wood, and metal. Objects can be described by the properties of the materials from which they are made ,and those properties can be used to separate or sort a group of objects or materials.

composition, group, object, separate, similarity, sort

Materials can exist in different states--solid, liquid, and gas. Some common materials, such as water, can be changed from one state to another by heating or cooling. 127 B (K-4)

transformation

Position and motion of objects

teaching standard

spatial concepts

The position of an object can be described by locating it relative to another object or the background.

background, location, object, position

An object's motion can be described by tracing and measuring its position over time. 127 B (K-4)

Cells have particular structures that underlie their functions. Every cell is surrounded by a membrane that separates it from the outside world. Inside the cell is a concentrated mixture of thousands of different molecules which form a variety of specialized structures that carry out such cell functions as energy production, transport of molecules, waste disposal, synthesis of new molecules, and the storage of genetic material. 184 C (9-12)

Most cell functions involve chemical reactions. Food molecules taken into cells react to provide the chemical constituents needed to synthesize other molecules. Both breakdown and synthesis are made possible by a large set of protein catalysts, called enzymes. The breakdown of some of the food molecules enables the cell to store energy in specific chemicals that are used to carry out the many functions of the cell. 184 C (9-12)

Cells store and use information to guide their functions. The genetic information stored in DNA is used to direct the synthesis of the thousands of proteins that each cell requires. 184 C (9-12)

storage, synthesis

Cell functions are regulated. Regulation occurs both through changes in the activity of the functions performed by proteins and the selective expression of individual genes. This regulation allows cells to respond to their environment and to control and coordinate the synthesis and breakdown of specific molecules, cell growth and division. 184 C (9-12)

Plant cells contain chloroplasts, the site of photosynthesis. Plants and many microorganisms use solar energy to combine molecules of carbon dioxide and water into complex, energy rich organic compounds and release oxygen to the environment. This process of photosynthesis provides a vital connection between the sun and the energy needs of living systems. 184 C (9-12)

Cells can differentiate, and complex multicellular organisms are formed as a highly organized arrangement of differentiated cells. In the development of these multicellular organisms, the progeny from a single cell form an embryo in which the cells multiply and differentiate to form the many specialized cells, tissues and organs that comprise the final organism. This differentiation is regulated through the expression of different genes. 184 C (9-12)

arrangement, differentiation, formation, multiplication, organization

Molecular basis of heredity

teaching standard

spatial concepts

In all organisms, the instructions for specifying the characteristics of the organism are carried in DNA, a large polymer formed from subunits of four kinds (A,G,C, and T). The chemical and structural properties of DNA explain how the genetic information that underlies heredity is both encoded in genes (as a string of molecular 'letters') and replicated (by a templating mechanism). Each DNA molecule in a cell forms a single chromosome. 185 C (9-12)

Most of the cells in a human contain two copies of each of 22 different chromosomes. In addition, there is a pair of chromosomes that determines sex: a female contains two X chromosomes and a male contains one X and one Y chromosome. Transmission of genetic information to offspring occurs through egg and sperm cells that contain only one representative from each chromosome pair. An egg and a sperm unite to form a new individual. The fact that the human body is formed from cells that contain two copies of each chromosome--and therefore two copies of each gene--explains many features of human heredity, such as how variations that are hidden in one generation can be expressed in the next. 185 C (9-12)

chromosome, containment, egg, sperm, transmission, unite

Changes in DNA (mutations) occur spontaneously at low rates. Some of these changes make no difference to the organism, whereas others can change cells and organisms. Only mutations in germ cells can create the variation that changes an organism's offspring. 185 C (9-12)

mutation

Biological evolution

teaching standard

spatial concepts

Species evolve over time. Evolution is the consequence of the interactions of (1) the potential for a species to increase its numbers, (2) the genetic variability of offspring due to mutation and recombination of genes, (3) a finite supply of the resources required for life, and (4) the ensuing selection by the environment of those offspring better able to survive and leave offspring. 185 C (9-12)

Living systems at all levels of organization demonstrate the complementary nature of structure and function. Important levels of organization for structure and function include cells, organs, tissues, organ systems, whole organisms, and ecosystems. 156 C (5-8)

All organisms are composed of cells--the fundamental unit of life. Most organisms are single cells; other organisms, including humans, are multicellular. 156 C (5-8)

cell, composition, multicellular, unit

Cells carry on the many functions needed to sustain life. They grow and divide, thereby producing more cells. This requires that they take in nutrients, which they use to provide energy for the work that cells do and to make the materials that a cell or an organism needs. 156 C (5-8)

absorption, divide, division, grow, growth

Specialized cells perform specialized functions in multicellular organisms. Groups of specialized cells cooperate to form a tissue, such as a muscle. Different tissues are in turn grouped together to form larger functional units, called organs. Each type of cell, tissue, and organ has a distinct structure and set of functions that serve the organism as a whole. 156 C (5-8)

The human organism has systems for digestion, respiration, reproduction, circulation, excretion, movement, control and coordination, and for protection from disease. These systems interact with one another. 156 C (5-8)

coordination, excretion, interaction, motion, movement, system

Disease is a breakdown in structures or functions of an organism. Some diseases are the result of intrinsic failures of the system. Others are the result of damage by infection by other organisms. 157 C (5-8)

decomposition, infection, structure

Reproduction is a characteristic of all living systems; because no individual organism lives forever, reproduction is essential to the continuation of every species. Some organisms reproduce asexually. Other organisms reproduce sexually. 157 C (5-8)

Reproduction and heredity

teaching standard

spatial concepts

In many species, including humans, females produce eggs and males produce sperm. Plants also reproduce sexually--the egg and sperm are produced in the flowers of flowering plants. An egg and sperm unite to begin the development of a new individual. That new individual receives genetic information from its mother (via the egg) and its father (via the sperm). Sexually produced offspring never are identical to either of their parents. 157 C (5-8)

production, receive, unite, uniting

Every organism requires a set of instructions for specifying its traits. Heredity is the passage of these instructions from one generation to another. 157 C (5-8)

passage

Hereditary information is contained in genes, located in the chromosomes of each cell. Each gene carries a single unit of information. An inherited trait of an individual can be determined by one or many genes, and a single gene can influence more than one trait. A human cell contains many thousands of different genes. 157 C (5-8)

Organisms have basic needs. For example, animals need air, water, and food; plants require air, water, nutrients, and light. Organisms can survive only in environments in which their needs can be met. The world has many different environments, and distinct environments support the life of different types of organisms. 129 C (K-4)

environment, world

Each plant or animal has different structures that serve different functions in growth, survival, and reproduction. For example, humans have distinct body structures for walking, holding, seeing, and talking. 129 C (K-4)

growth, holding, seeing, structure, walking

The behavior of individual organisms is influenced by internal cues (such as hunger) and by external cues (such as a change in the environment). Humans and other organisms have senses that help them detect internal and external cues. 129 C (K-4)

containment, environment, external, internal

Life cycles of organisms

teaching standard

spatial concepts

Plants and animals have life cycles that include being born, developing into adults, reproducing, and eventually dying. The details of this life cycle are different for different organisms. 129 C (K-4)

cycle, development

Plants and animals closely resemble their parents. 129 C (K-4)

resemblance

Many characteristics of an organism are inherited from the parents of the organism, but other characteristics result from an individual's interactions with the environment. Inherited characteristics include the color of flowers and the number of limbs of an animal. Other features, such as the ability to ride a bicycle are learned through interactions with the environment and cannot be passed on to the next generation. 129 C (K-4)

environment, interaction

Organisms and environments

teaching standard

spatial concepts

All animals depend on plants. Some animals eat plants for food. Other animals eat animals that eat the plants. 129 C (K-4)

An organism's patterns of behavior are related to the nature of that organism's environment, including the kinds and numbers of other organisms present, the availability of food and resources, and the physical characteristics of the environment. When the environment changes, some plants and animals survive and reproduce, and others die or move to new locations. 129 C (K-4)

Earth systems have internal and external sources of energy, both of which create heat. The sun is the major external source of energy. Two primary sources of internal energy are the decay of radioactive isotopes and the gravitational energy from the earth's original formation.

decay, external, formation, gravity, internal, source

The outward transfer of earth's internal heat drives convection circulation in the mantle that propels the plates comprising earth's surface across the face of the globe. 189 D (9-12)

Heating of earth's surface and atmosphere by the sun drives convection within the atmosphere and oceans, producing winds and ocean currents. 189 D (9-12)

convection, current, surface, wind, within

Global climate is determined by energy transfer from the sun at and near the earth's surface. This energy transfer is influenced by dynamic processes such as cloud cover and the earth's rotation, and static conditions such as the position of mountain ranges and oceans. 189 D (9-12)

The earth is a system containing essentially a fixed amount of each stable chemical atom or element. Each element can exist in several different chemical reservoirs. Each element on earth moves among reservoirs in the solid earth, oceans, atmosphere, and organisms as part of geochemical cycles. 189 D (9-12)

cycle, motion, movement, quantity, reservoir, system

Movement of matter between reservoirs is driven by the earth's internal and external sources of energy. These movements are often accompanied by a change in the physical and chemical properties of the matter. Carbon, for example, occurs in carbonate rocks such as limestone, in the atmosphere as carbon dioxide gas, in water as dissolved carbon dioxide, and in all organisms as complex molecules that control the chemistry of life .

The sun, the earth, and the rest of the solar system formed from a nebular cloud of dust and gas 4.6 billion years ago. The early earth was very different from the planet we live on today. 189 D (9-12)

formation, nebular, solar system, system

Geologic time can be estimated by observing rock sequences and using fossils to correlate the sequences at various locations. Current methods include using the known decay rates of radioactive isotopes present in rocks to measure the time since the rock was formed. 189 D (9-12)

Interactions among the solid earth, the oceans, the atmosphere, and organisms have resulted in the ongoing evolution of the earth system. We can observe some changes such as earthquakes and volcanic eruptions on a human time scale, but many processes such as mountain building and plate movements take place over hundreds of millions of years. 189 D (9-12)

Evidence for one-celled forms of life--the bacteria--extends back more than 3.5 billion years. The evolution of life caused dramatic changes in the composition of the Earth's atmosphere, which did not originally contain oxygen. 190 D (9-12)

Global patterns of atmospheric movement influence local weather. Oceans have a major effect on climate, because water in the oceans holds a large amount of heat. 160 D (5-8)

containment, formation, global, local, movement, pattern

Living organisms have played many roles in the earth system, including affecting the composition of the atmosphere, producing some types of rocks, and contributing to the weathering of rocks. 160 D (5-8)

composition, weathering

Lithospheric plates on the scales of continents and oceans constantly move at rates of centimeters per year in response to movements in the mantle. Major geological events, such as earthquakes, volcanic eruptions, and mountain building, result from these plate motions. 160 D (5-8)

Land forms are the result of a combination of constructive and destructive forces. Constructive forces include crustal deformation, volcanic eruption, and deposition of sediment, while destructive forces include weathering and erosion. 160 D (5-8)

Some changes in the solid earth can be described as the 'rock cycle.' Old rocks at the earth's surface weather, forming sediments that are buried, then compacted, heated, and often recrystallized into new rock. Eventually, these new rocks may be brought to the surface by the forces that drive plate motions, and the rock cycle continues. 160 D (5-8)

buried, compaction, cycle, force, formation, motion, plate, surface

Soil consists of weathered rocks, decomposed organic material from dead plants, animals, and bacteria. Soils are often found in layers, with each having a different chemical composition and texture. 160 D (5-8)

composition, layer, texture

Water, which covers the majority of the earth's surface, circulates through the crust, oceans, and atmosphere in what is known as the 'water cycle.' Water evaporates from the earth's surface, rises and cools as it moves to higher elevations, condenses as rain or snow, and falls to the surface where it collects in lakes, oceans, soil, and in rocks underground. 160 D (5-8)

Earth materials are solid rocks and soils, water, and the gases of the atmosphere. These varied materials have different physical and chemical properties, which make them useful in different ways, for example, as building materials, as sources of fuel, or for growing the plants we use as food. Earth materials provide many of the resources that humans use. 134 D (K-4)

Soils have properties of color and texture, capacity to retain water, and ability to support the growth of many kinds of plants, including those in our food supply. 134 D (K-4)

growth, property, texture

Fossils provide evidence about the plants and animals that lived long ago and nature of the environment at that time. 134 D (K-4)

environment, evidence, fossil, timeline

Objects in the sky

teaching standard

spatial concepts

The sun, moon, stars, clouds, birds, and airplanes all have properties, locations, and movements that can be observed and described. 134 D (K-4)

location, movement, property

The sun provides the light and heat necessary to maintain the temperature of the earth. 134 D (K-4)

position

Changes in earth and sky

teaching standard

spatial concepts

The surface of the earth changes. Some changes are due to slow processes, such as erosion and weathering, and some changes are due to rapid processes such as landslides, volcanoes, and earthquakes. 134 D (K-4)

Weather changes from day to day and over the seasons. Weather can be described by measurable quantities, such as temperature, wind direction and speed, and precipitation. 134 D (K-4)

direction, measurement, movement, precipitation, speed, temperature

Objects in the sky have patterns of movement. The sun, for example, appears to move across the sky in the same way every day, but its path changes slowly over the seasons. The moon moves across the sky on a daily basis much like the sun. The observable shape of the moon changes from day to day in a cycle that lasts about a month. 134 D (K-4)